A. Field of the Invention
The invention relates to a damper disk assembly, and particularly a damper disk assembly for transmitting a torque and for absorbing and damping a torsional vibration.
B. Description of the Background Art
A clutch disk assembly used in a clutch of a vehicle has a clutch function for releasable engagement with a flywheel, and also has a damper function for damping a torsional vibration. The clutch disk assembly includes a clutch coupling portion, an input plate fixed to the clutch coupling portion, a hub disposed radially inside the input plate, and elastic members elastically coupling the input plate to a flange of the hub in a circumferential direction. When the clutch coupling portion is coupled to the flywheel, torque is supplied to the clutch disk assembly from the flywheel. Torque is transmitted to the hub via the elastic members, and then is output to a shaft extending from a transmission. When variations in torque of the engine is transmitted to the clutch disk assembly, relative rotation occurs between the input plate and the hub, and the elastic members are repetitively and circumferentially compressed. The clutch disk assembly further includes a friction mechanism which is arranged between the input plate and the hub for generating a frictional resistance when the relative rotation occurs therebetween. The friction mechanism is formed of a plurality of washers, a biasing member and others.
In a clutch disk assembly of a hub-separate type, the flange is separate from the hub, and is used as an intermediate member. The hub and the intermediate member are circumferentially coupled together by elastic members having a low rigidity. In this clutch disk assembly, a maximum torsional angle between the input plate and the hub can be increased, and operation characteristics can have two stages of low and high rigidities.
In a torsional vibration system that operates with the clutch disk assembly, for instance the transmission and other components of the drive system, normal vibrations in rotation speed of the engine continuously cause collision between teeth of paired gears in the transmission, and thereby cause noises sometimes referred to as idle rattle. For reducing the torsional vibration causing the gear noises in the clutch disk assembly, it is necessary to reduce a spring constant of the elastic members of a low rigidity for the first stage. However, for damping the torsional vibration such as a low frequency vibration, which causes the relative rotation of a large angle, it is necessary to increase a spring constant of the elastic members functioning in the second state. In the conventional device having such characteristics, a jumping phenomenon occurs. In other words, the operation angle jumps over between the first stage and second stage, for example, when a torque variation is supplied during idling. The jumping phenomenon is caused by oscillations in transmission of the inertia with respect to the elastic members which are provided in the clutch disk assembly for the second stage of dampening characteristics, and causes gear collision to an extent higher than the normal gear collision due to excessive rotational variations.